Island pack as scenery pack can have themes like beach, Caribbean, pirate, Hawaii, etc., Something like that. I personally want highland/mountain and tropical/rainforest pack as animal pack since it's biome pack. If it's scenery, mountain pack can work as having Himalayan themes (Villages in Himalaya and Nepal/Bhutan theme) as they have beautiful buildings and architecture along with more rocks which would be nice and some more mountain vegetations.
Tropical Rainforest as scenery pack probably will be similar to SA pack, but with much more foliage which would be amazing and more building pieces based on architecture and buildings in tropical rainforest around the world (Not just SA, including African Rainforest, Asian Rainforest, etc.)
I do get that if those packs are scenery may will leave people wanting more animals, same thing as me with conservation pack, it's a great pack with amazing building pieces, but for me it could've been animal pack with more endangered animals in it like pere david deer, black rhino, tasmanian devil, addax, etc.